CANBERRA, Australia – More than 90% of Great Barrier Reef corals surveyed this year were bleached in the fourth mass event in seven years in the world’s largest coral reef ecosystem, Australian government scientists have said.
The bleaching is caused by global warming, but it is the first reef bleaching event during a La Niña weather pattern, which is associated with cooler Pacific Ocean temperatures, the Great Barrier Reef Marine Authority said. in its annual report published on Tuesday evening which revealed that 91% of the areas surveyed had been affected.
Bleaching in 2016, 2017 and 2020 damaged two-thirds of the corals in the famed reef off the east coast of Australia.
Coral is bleaching in response to heat stress and scientists hope most corals will recover from the current event, said David Wachenfeld, chief scientist at the authority, which manages the reef ecosystem.
“Early indications are that the mortality will not be very high,” Wachenfeld said on Wednesday.
“Hopefully we’ll see most of the bleached corals recover and we’ll end up with an event a bit more like 2020 when, yes, there was massive bleaching, but there was low mortality,” Wachenfeld added. .
The 2016 and 2017 bleaching events resulted in “pretty high levels of coral mortality,” Wachenfeld said.
Simon Bradshaw, a researcher at the Climate Council, an Australia-based group that tracks climate change, said the report demonstrated the reef’s survival depended on deep reductions in global emissions over the decade.
“It’s heartbreaking. It’s deeply disturbing,” Bradshaw said. “It shows that our coral reef is in really, really serious trouble.”
Last December, the first month of Southern Hemisphere summer, was the warmest December the reef has seen since 1900. A ‘marine heat wave’ set in in late February, the report said. .
A United Nations delegation visited the reef in March to assess whether the reef’s World Heritage listing should be downgraded due to the ravages of climate change.
In July last year, Australia garnered enough international support to postpone an attempt by UNESCO, the United Nations cultural organization, to downgrade the reef’s World Heritage status to ‘endangered’ due damage caused by climate change.
But the issue will be back on the agenda of the World Heritage Committee at its next annual meeting.
The Great Barrier Reef represents about 10% of the world’s coral reef ecosystems and was named because of the considerable risks it posed to 18th century sailors. The network of over 2,500 reefs covers 348,000 square kilometers (134,000 sq mi).
Coral is made up of tiny animals called polyps that feed on microscopic algae that live inside reefs and are sensitive to changes in water temperature.
Algae provide the reefs with their kaleidoscope of colors and produce sugars through photosynthesis which provide the coral with most of its nutrients.
Rising ocean temperatures turn chemicals produced by algae into toxins. The coral turns white as it effectively spits out toxic algae.
Heat stress beyond a few weeks can lead the coral to starve.
The latest whitewash is an unwelcome reminder of the policy differences on climate change among Australian politicians.
The Conservative government seeking re-election on May 21 has less ambitious emissions reduction targets than the centre-left opposition promises.
Prime Minister Scott Morrison’s Liberal Party aims to cut Australia’s emissions by 26-28% below 2005 levels by 2030.
The opposition Labor Party has promised to cut emissions by 43% by the end of the decade.
Morrison was widely criticized at the United Nations climate conference last November for failing to set a more ambitious target.
Environmental group Greenpeace Australia Pacific said in a statement that the scale of the latest bleaching was “another damning accusation of the Morrison government failing to protect the reef and exacerbating the problem by supporting fossil fuels”.